FIELD OF THE INVENTION
The invention relates to a cylinder or roller having a base body formed of fiber-reinforced plastic and a wear-resistant layer at least partially covering the outer roller surface or casing. The invention also relates to a method for producing such a cylinder or roller. The invention relates in particular to rollers or cylinders of the indicated type for the purpose of web guiding and deflecting, for transporting or for rolling and unrolling webs of paper, film or material.
When manufacturing and processing paper, plastics or other materials in the form of webs, cylinders of metal or of plastic reinforced with fibers are used today for transporting, guiding, deflecting and rolling or unrolling. Metallic cylinders can be produced with high precision at comparatively reasonable cost. The surface thereof can easily be adapted to the respective requirements with regard to surface roughness, surface hardness, and abrasion or corrosion behavior. The disadvantage of that type of cylinder lies in its large mass and therefore its inertia. As a result, metal cylinders are subjected to high centrifugal forces with the danger of deformation or unsteady operation, the driving forces are comparatively high and high demands are made on the mechanical balance. Moreover, the large mass of such cylinders has to be considered in the structural planing of the machines and installations, and results in correspondingly heavy and therefore expensive frame, bearing and drive structures. Cylinders that are formed of plastic reinforced with fibers, especially carbon fibers, do not have those drawbacks. Such cylinders, as compared with metal cylinders with an identical bending resistance, improved retention of shape and good resistance to corrosion, have a substantially smaller mass, which offers substantial advantages in the dynamic characteristics and in the configuration of the installation (see German Petty Patent DE-GM 83 22 639, corresponding to U.S. Pat. No. 4,586,224). A substantial disadvantage of fiber-reinforced plastic cylinders is their low resistance to abrasion. In order to overcome that problem, methods for coating the surfaces of such cylinders have been developed, with the aid of which it has been possible for single or multi-layered metallic or even ceramic coatings to be produced on the outer surface of the cylinders, which met the demands of competitive metallic cylinders with regard to the resistance to abrasion in combination with other surface properties, e.g. roughness, structure or electric conductivity. In order to apply such suitable coatings, in addition to electrolytic methods (as in German Petty Patent DE-GM 84 06 019.0), thermal spraying methods such as plasma spraying or flame-spraying, have been used almost exclusively. Such methods are found in British Patent No. 887 366; Swiss Patent CH 538 549, corresponding to U.S. Pat. No. 3,775,208; German Patent DE 35 27 912 C2; or German Patent DE 38 44 290 C1, corresponding to Published European Application No. 0 375 914 A1. All of the coatings according to those methods require high expenditure, but nevertheless the bond strength and impact resistance of the coated layers are often not completely satisfactory. In addition, those circumstances have resulted in the use of fiber-reinforced cylinders, which are desirable per se, but have not yet found an opening in industrial technology to the extent that would be expected because of the excellent weight related mechanical strength properties of that advanced cylinder material.